1. Field of the Invention
The present invention relates to hypodermic syringes, and more particularly, to a hypodermic syringe with a needle which retracts into a protective sleeve, and a related method.
2. Description of Related Art
Hypodermic syringes having a variety of designs to shield the needle after use are disclosed in the art. Various shields are disclosed, as well as syringes having needle assemblies which retract into an outer sleeve also referred to as a shield or sheath. Syringes are also disclosed having needles which retract into the syringe barrel or plunger.
A syringe is disclosed in U.S. Pat. No. 5,106,379 which comprises a cylindrical syringe barrel having a needle secured at one end. A plunger is slidingly received within the interior barrel chamber. A boss extendes radially outward from the cylindrical syringe barrel. There is sheath slidingly positioned on the cylindrical syringe barrel. The sheath is movable between a retracted needle exposing position and an extended needle surrounding position. The sheath has a slot to receive the boss. The slot includes a longitudinal portion extending parallel to the axis of the syringe barrel and a laterally extending portion extending laterally with respect to the cylindrical syringe barrel. The laterally extending protion is on the end of the groove opposite the needle. A spring biasingly urges the sheath toward the extended needle surrounding position. The spring is secured to the cylindrical syringe barrel and the sheath such that the spring biasingly rotates the boss into a laterally extending portion of the slot as the sheath is advanced to the extended needle surrounding position. When the boss is positioned in the laterally extending portion of the slot the sheath cannot be retracted due to the axial forces acting on the sheath. There is a restraining means for selectively restraining the sheath in the needle exposing position. A restraining means is disclosed to be a barb attached to the cylindrical syringe barrel. The sheath includes a barb receiving aperture such that when the sheath is advanced to the needle exposing position the barb receiving aperture captures the barb so as to prevent the sheath from being advanced to the extended needle surrounding position. A release means selectively releases the sheath from the restraining means to allow the spring to advance the sheath to the extended needle surrounding position. A trigger is secured to the sheath and can be used to move the barb receiving aperture away from the barb such that the barb does not prevent the spring from biasingly urging the sheath to the extended needle surrounding position.
U.S. Pat. No. 5,024,660 discloses a syringe having a barrel with a needle mounted on one end. A piston is mounted for movement longitudinally within the barrel. There is a tubular sleeve dimensioned to fit over the barrel. A longitudinal groove is along the outside of the barrel. The groove has lateral extensions at both ends. The sleeve has an internal projection which extends into the groove. The sleeve can be locked in to a retracted position or an extended position. The syringe is operated by hand with no automatic feature to cause the sleeve to extend around and shield the needle.
U.S. Pat. No. 5,061,251 discloses a syringe having a movable shield between a first position for shielding a needle and a second position for shielding the needle member. There is a means for manually moving the shield member from the first to the second position. A spring means normally biases the shield member in the shielding position.
U.S. Pat. No. 5,057,087 discloses a syringe barrel, a needle extending from the barrel, a needle extending from the barrel, a movable safety sleeve surrounding the barrel, and a sleeve cap to cover the forward end of the sleeve. The syringe barrel includes a forward detent, an intermediate detent, and a rear detent. The safety sleeve also includes an inner ring for selective engagement with the detents. The safety sleeve is axially movable on the syringe barrel from an initial transport position on the intermediate detent, to a retracted position on the rear detent to expose the needle, and to a locked safety position on the forward detent. The sleeve cap is held on the safety sleeve by friction when the sleeve is in the transport position, and by positive engagement with the safety sleeve when the sleeve is in the locked safety position.
U.S. Pat. Nos. 4,998,920 and 5,066,277 discloses syringes where the needle is located in a protective sleeve after use.
A continuing goal in the art is automatic retraction of the needle into a protected position. Many attempts have been made to retract the needle using a spring including those disclosed in U.S. Pat. Nos. 4,994,034; 5,000,736; 5,017,187; 5,019,044; 5,026,353; 5,049,133 and 5,064,419.
Other patents of interest disclosing syringes with retractable needles include U.S. Pat. Nos. 5,019,043; 5,026,354; 5,030,208 and 5,066,280. Patents of interest which disclose single use needles include U.S. Pat. Nos. 5,066,281 and 5,067,942.
Generally, the art discloses that there has been a continuing interest to develop a syringe which has a needle that can be retracted to prevent accidental needle pricks to the patients and to persons administering injections. Given the circumstances surrounding injections and needle disposal it desireable for the needle to automatically retract. Preferably, there should be a minimum of additional steps to cause needle retraction by the person administering the injection. Such an improvement is desireable for syringes contemplated for single or multiple uses.